SAN ANTONIO — The English call them “engine rooms,” versatile and tireless midfielders who roam from penalty box to penalty box, creating offensive chances while also tracking back to help out on defense.

They are exceedingly valuable, particularly at a level like the North American Soccer League. And the Scorpions have one in Colombia's Rafael “Rafa” Castillo.

The NASL Player of the Month for July has been a revelation since joining the club before the start of the fall season. Castillo scored three goals in his first four matches, all victories, while the Scorpions outscored their foes 9-1.

They came crashing back to earth with an embarrassing 3-1 loss at Edmonton last weekend.

There were multiple factors, not least of which was the 14 hours it took to reach their destination. But it couldn't have been a coincidence that the Scorpions fell apart without Castillo, who was forced to remain in Texas after the team failed to secure a visa.

His return won't come a moment too soon as the Scorpions (4-0-1, 12 points), still in first place, attempt get back on track Saturday night at Toyota Field against Indy Eleven (2-1-2, seven points).

“He's like a (Marcos) Senna for (the New York) Cosmos, a difference-maker,” Scorpions manager Alen Marcina said. “Every time they touch the ball, something seems to happen. Rafa is one of those players.”

Having made nine appearances for Colombia's senior national team in his early 20s, Castillo arrived on Marcina's radar via a tip from Scorpions winger and fellow Colombian Walter Restrepo. He remained on trial with the Scorpions for roughly a month until they were able to add him to the roster.

It doesn't seem possible that such an undersized player — at only 5-foot-3 and 143 pounds, Castillo is invariably the smallest on the pitch — could provide such a strong presence. But Castillo, speaking through a translator, said he learned a long time ago to overcome that shortcoming with guile and nonstop effort.